1. Field of the Invention
The invention relates to an apparatus for measuring out-of-roundness of a cylindrical object, such as a metal bar or tube.
2. Description of the Prior Art
In various production processes for making or reshaping cylindrical objects, such as bars, pipe and tubing, it is desirable to monitor the degree of roundness of the object either during or at the conclusion of a production process.
Conventionally, this is achieved by manually withdrawing the workpiece from the production line and inspecting it for roundness at a plurality of locations along the length thereof. This examination is performed by a hand-manipulated micrometer. For this purpose it is customary to use conventional v-anvil micrometer calipers. With this practice, however, the workpiece must be stationary to be measured. In addition, the micrometer generally must be slipped onto the workpiece from an end thereof. In the case where the workpiece is an elongated cylindrical object, such as bar, pipe or tubing, that is supported along the length thereof the workpiece must in this instance be progressively lifted as the micrometer passes by each supporting member thereof.
It is also known to use a series of parallel light beams directed across the path of a moving workpiece and provide a receiving device opposite the light source to measure the dimensions of a shadow created by the workpiece passing through the light beams. Although this practice permits the measurement of the dimensions of a workpiece, it is not suitable for use in determining out-of-roundness. This results from the fact that typically out-of-roundness of workpieces is characterized by a series of projections and opposed depressions about the circumference of the workpiece. Conventional diametrical measurements are not effective, because during measurement a depression offsets any value obtained with respect to an opposed projection.